post-merge build is broken

Seems it doesn't like something about tcmalloc
```
Use --sandbox_debug to see verbose messages from the sandbox
warning: unknown warning option '-Wno-implicit-int-float-conversion'; did you mean '-Wno-implicit-float-conversion'? [-Wunknown-warning-option]
In file included from external/com_github_google_tcmalloc/tcmalloc/cpu_cache.cc:15:
In file included from external/com_github_google_tcmalloc/tcmalloc/cpu_cache.h:30:
external/com_github_google_tcmalloc/tcmalloc/internal/percpu_tcmalloc.h:332:18: error: invalid output constraint '=@ccae' in asm
[overflow] "=@ccae"(overflow)
^
external/com_github_google_tcmalloc/tcmalloc/internal/percpu_tcmalloc.h:459:25: error: invalid output constraint '=@ccbe' in asm
[underflow] "=@ccbe"(underflow),
^
1 warning and 2 errors generated.
Target //:envoy failed to build
INFO: Elapsed time: 52.329s, Critical Path: 21.65s
INFO: 2526 processes: 2130 internal, 395 processwrapper-sandbox, 1 worker.
FAILED: Build did NOT complete successfully
FAILED: Build did NOT complete successfully
```

did a bit of bisecting and I think it started with this commit in main Envoy: https://github.com/envoyproxy/envoy/commit/4c0d2d2a36996f2ec7d00b519ea90068629a2c55'

envoy-filter-example commit: https://github.com/envoyproxy/envoy-filter-example/commit/db2cdca49e2546eca58006c3a01f1b3e8777f39d